Combined directed ortho metalation -: intramolecular Friedel-Crafts connections.: Regiospecific route to 1-substituted fluoren-9-ones

ortho-Substituted-2-biphenyl carboxylic acids of the type 3a-j were prepared by the tandem metalation sequence from 2-biphenyl carboxylic acid 1 with sec-butyllithium in THF at -78degreesC followed by quenching with electrophiles. The carboxylic acids 3a-f were converted into 1-substituted fluorenones 4a-f upon treatment with methanesulfonic acid. (C) 2002 Elsevier Science Ltd. All rights reserved.